const fp = require('lodash/fp')
class Container {
	static of(value) {
		return new Container(value)
	}
	constructor(value) {
		this._value = value
	}
	map(fn) {
		return Container.of(fn(this._value))
	}
}

class Maybe {
	static of(x) {
		return new Maybe(x)
	}
	isNothing() {
		return this._value === null || this._value === undefined
	}
	constructor(x) {
		this._value = x
	}
	map(fn) {
		return this.isNothing() ? this : Maybe.of(fn(this._value))
	}
}
// let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do'])
// let ex2=(x)=> Maybe.of(fp.first(x._value))._value


// console.log(ex2(xs))
// let safeProp = fp.curry(function(x, o){
//     return Maybe.of(o[x])
// })
// let user = { id: 2, name: 'Albert' }
// let ex3 = ()=> fp.first(safeProp("name",user)._value)

// console.log(ex3())
// let ex4 = function(n){
//     if(n){
//         return parseInt(n)
//     }
// }
let ex4=(n)=>Maybe.of(n).map(n=>parseInt(n))._value
console.log(ex4(4))